Nutrition is the biochemical
process by which an organism
to support its life. It includes ingestion
that studies the physiological process of nutrition is called nutritional science
(also ''nutrition science'').
Organism primarily provide themselves with carbon in one of two ways: autotrophy
(the self-production of organic food) and heterotrophy
(the consumption of existing organic carbon). Combined with the source of energy, either light (phototrophy
) or chemical (chemotrophy
), there are four primary nutritional groups for organisms.
''Nutrients'' are substances used by an organism to survive, grow, and reproduce. The seven major classes of relevant nutrients for animals (including humans) are carbohydrates
s, and water
. Nutrients can be grouped as either macronutrients
(needed in larger quantities) or micronutrients
(needed in small quantities).
In nutrition, the ''diet'' of an organism is the sum of foods it eats, which is largely determined by the availability and palatability
''Human nutrition'' deals with the provision of essential nutrient
s in food that are necessary to support human life
and good health
In humans, poor nutrition can cause deficiency-related diseases such as blindness
, preterm birth
or nutrient excess health-threatening conditions such as obesity
and metabolic syndrome
; and such common chronic systemic diseases as cardiovascular disease
, and osteoporosis
. Undernutrition can lead to wasting
in acute cases, and the stunting
in chronic cases of malnutrition
''Animal nutrition'' focuses on the dietary nutrients needs of animals
, often in comparison (or contrast) to other organisms like plants. Carnivore
diets are contrasting, with basic nitrogen
proportions vary for their particular foods. Many herbivores rely on bacterial fermentation to create digestible nutrients from indigestible plant cellulose, while obligate carnivores must eat animal meats to obtain certain vitamins or nutrients their bodies cannot otherwise synthesize. Animals generally have a higher requirement of energy in comparison to plants.
''Plant nutrition'' is the study of the chemical element
s that are necessary for plant growth. There are several principles that apply to plant nutrition. Some elements are directly involved in plant metabolism
. However, this principle does not account for the so-called beneficial elements, whose presence, while not required, has clear positive effects on plant growth.
A nutrient that is able to limit plant growth according to Liebig's law of the minimum
is considered an essential plant nutrient if the plant cannot complete its full life cycle without it. There are 16 essential plant soil nutrients, besides the three major elemental nutrients carbon and oxygen that are obtained by photosynthetic plants from carbon dioxide in air, and hydrogen
, which is obtained from water.
Plants uptake essential elements from the soil
through their root
s and from the air (consisting of mainly nitrogen and oxygen) through their leaves
. Green plants obtain their carbohydrate supply from the carbon dioxide in the air by the process of photosynthesis
. Carbon and oxygen are absorbed from the air, while other nutrients are absorbed from the soil. Nutrient uptake in the soil is achieved by cation exchange
, wherein root hair
s pump hydrogen ion
) into the soil through proton pump
s. These hydrogen ions displace cation
s attached to negatively charged soil particles so that the cations are available for uptake by the root. In the leaves, stomata
open to take in carbon dioxide and expel oxygen
. The carbon dioxide molecules are used as the carbon source in photosynthesis.
is plentiful in the Earth's atmosphere, very few plants can use this directly. Most plants, therefore, require nitrogen compounds to be present in the soil in which they grow. This is made possible by the fact that largely inert atmospheric nitrogen is changed in a nitrogen fixation
process to biologically usable forms in the soil by bacteria.
[Lindemann, W.C. and Glover C.R. (2003]
Nitrogen Fixation by Legumes
New Mexico State University/
is a difficult subject to understand completely, partially because of the variation between different plants and even between different species or individuals of a given clone
. Elements present at low levels may cause deficiency symptoms, and toxicity is possible at levels that are too high. Furthermore, deficiency of one element may present as symptoms of toxicity from another element, and vice versa.
* Nutrition psychology
* Physical fitness
* Curley, S., and Mark (1990). ''The Natural Guide to Good Health'', Lafayette, Louisiana, Supreme Publishing
Diet, Nutrition and the prevention of chronic diseases
by a Joint WHO
Expert consultation (2003)
UN Standing Committee on Nutrition
– In English, French and Portuguese